Josh,
I agree to treat this case as a (1) convinence.
But it is still very cpecific, more than just simplifying FKs
And you have said about general GUID problem.
Let we disscuss this problem ? I hope to here good ideas from you again.
Now I solve the GUID problem, with one sequence of IDs on the main server.
The clients ask the server to lease some IDs via special (application-layer)
protocol. Server remembers who and when and what IDs have took.
(in terms of segments [a..b],[c..d]... etc)